全文获取类型
收费全文 | 881篇 |
免费 | 35篇 |
国内免费 | 8篇 |
专业分类
化学 | 508篇 |
晶体学 | 6篇 |
力学 | 21篇 |
数学 | 164篇 |
物理学 | 225篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 27篇 |
2013年 | 47篇 |
2012年 | 56篇 |
2011年 | 80篇 |
2010年 | 44篇 |
2009年 | 31篇 |
2008年 | 49篇 |
2007年 | 59篇 |
2006年 | 76篇 |
2005年 | 59篇 |
2004年 | 64篇 |
2003年 | 51篇 |
2002年 | 28篇 |
2001年 | 16篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1969年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有924条查询结果,搜索用时 216 毫秒
151.
Richard D. Chambers Christopher Farren Graham Sandford Dmitri S. Yufit Judith A. K. Howard 《无机化学与普通化学杂志》2002,628(8):1857-1860
Free radicals derived from some alkyl substituted cyclohexanol derivatives react with hexafluoropropene to give a variety of polyfluoroalkylated adducts. Stereochemistry of the processes is discussed and remote functionalisation of the methyl group in 2‐methylcyclohexanol by an unusual intramolecular hydrogen atom transfer process is reported. 相似文献
152.
Dmitri V. Konarev Alexey V. Kuzmin Salavat S. Khasanov Alexey A. Goryunkov Victor A. Brotsman Ilya N. Ioffe Akihiro Otsuka Hideki Yamochi Hiroshi Kitagawa Rimma N. Lyubovskaya 《化学:亚洲杂志》2019,14(11):1958-1964
Radical anion salt {cryptand[2.2.2] (K+)}2(bispheroid)2??3.5C6H4Cl2 ( 1 ) of the double‐caged fullerene C60 derivative, in which fullerene cages are linked by a cyclobutane bridging cycle and additionally by a pyrrolizidine moiety, was obtained. Each fullerene cage in this derivative accepts one electron on reduction, thus forming the (bispheroid)2? dianions with two interacting S=1/2 spins on the neighboring cages. Low‐temperature magnetic measurements reveal a singlet ground state of the bispheroid dianions whereas triplet contributions prevail at increased temperature. An estimated exchange interaction between two spins J/kB=?78 K in 1 indicates strong magnetic coupling between them, nearly two times higher than that (J/kB=?44.7 K) in previously studied (C60?)2 dimers linked via a cyclobutane bridge only. The enhancement of magnetic coupling in 1 can be explained by a shorter distance between the fullerene cages and, possibly, an additional channel for the magnetic exchange provided by a pyrrolizidine bridge. Quantum‐chemical calculations of the lowest electronic state of the dianions by means of multi‐configuration quasi‐degenerate perturbation theory support the experimental findings. 相似文献
153.
Dmitri B. Strukov R. Stanley Williams 《Applied Physics A: Materials Science & Processing》2009,94(3):515-519
We investigate the exponential dependence of switching speeds in thin-film memristors for high electric fields and elevated
temperatures. An existing nonlinear ionic drift model and our simulation results explain the very large ratios for the state
lifetime to switching speed experimentally observed in devices for which resistance switching is due to ion migration. Given
the activation barriers of the drifting species, it is possible to predict the volatility and switching time for various material
systems. 相似文献
154.
Dmitri E. Kharzeev 《The European Physical Journal C - Particles and Fields》2009,61(4):675-682
The apparent universality of jet quenching observed in heavy-ion collisions at RHIC for light and heavy quarks, as well as
for quarks and gluons, is very puzzling and calls for a theoretical explanation. Recently, it has been proposed that synchrotron-like
radiation at strong coupling gives rise to a universal bound on the energy of a parton escaping from the medium. Since this
bound appears to be quite low, almost all of the observed particles at high transverse momentum have to originate from the
surface of the hot fireball. Here I make a first attempt of checking this scenario against the RHIC data and formulate a “universal-bound
model” of jet quenching that can be further tested at RHIC and LHC. 相似文献
155.
Alex Greilich Dmitri R. Yakovlev Manfred Bayer 《Solid State Communications》2009,149(35-36):1466-1471
We address the precession of an ensemble of electron spins, each confined in a (In, Ga)As/GaAs self-assembled quantum dot. The quantum dot inhomogeneity is directly reflected in the precession of the optically oriented electron spins about an external magnetic field, which is subject to fast dephasing on a nanoseconds time scale. Proper periodic laser excitation allows synchronization of the electron spin precessions with the excitation cycle. The experimental conditions can be tailored such that eventually all (about a million) electron spins that are excited by the laser precess with a single frequency. In this regime the ensemble can be exploited during the single electron spin coherence times being in the microseconds range. 相似文献
156.
157.
Li C Winnard PT Takagi T Artemov D Bhujwalla ZM 《Journal of the American Chemical Society》2006,128(47):15072-15073
The conjugate of bacterial cytosine deaminase (bCD) and poly-l-lysine (PLL) that was functionalized with biotin, rhodamine, and Gd3+-DOTA was synthesized and characterized. It demonstrated high relaxivity, improved enzymatic specificity to prodrug 5-fluorocytosine, low cytotoxicity, efficient cell uptake, and high enzymatic stability in fresh mouse serum and human breast cancer cell culture. 相似文献
158.
Binucleating behavior of rigid triptycene-based ligands has been studied. It has been demonstrated that trans-spanned transition-metal mononuclear complexes bearing 1,8-bis(diisopropylphosphino)triptycene (L1) and 1-diisopropylphosphino-8-diphenylphosphinotriptycene (L2) react with an appropriate transition-metal precursor via a ring-expansion pathway to form unusual bimetallic quasi-closed structures. New palladium and rhodium complexes featuring strongly bent (ca. 115 degrees ) M2(mu-Cl2) cores with very closely spanned metal centers (less than 3 A) have been prepared using the described ring-expansion reaction and have been fully characterized. Despite a constrained arrangement of the binuclear system, halogen bridges in all new compounds were stable in both the solid state and solution showing no tendency for dissociation even in the presence of added Lewis bases. Spontaneous resolution of the dissymmetric Pd2(mu-Cl)2Cl2(1-diisopropylphosphino-8-diphenylphosphinotriptycene) (2) into enantiopure antipodes is discussed as well. 相似文献
159.
Petrovykh DY Kimura-Suda H Opdahl A Richter LJ Tarlov MJ Whitman LJ 《Langmuir : the ACS journal of surfaces and colloids》2006,22(6):2578-2587
We have studied the formation of self-assembled monolayers (SAMs) of n-alkanethiols on platinum thin films using X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and contact angle (CA) measurements. Specifically, SAMs of 1-hexanethiol, 1-dodecanethiol, and 1-octadecanethiol were grown on polycrystalline Pt films, and the effects of Pt surface preparation, deposition conditions, and solvent treatments on the initial quality and stability of the monolayer in air were investigated. The SAMs prepared under ambient conditions on piranha-cleaned and UV/ozone-cleaned substrates were compared to monolayers formed on template-stripped Pt in an inert atmosphere. We found that alkanethiols deposited from 1 mM ethanolic solutions on piranha-cleaned Pt formed densely packed monolayers in which alkyl chains were oriented close to the surface normal. Stored in the laboratory ambient, these monolayers were unchanged over about 1 week but were largely oxidized in about 1 month. No evidence was found of molecules being weakly bound within the monolayer or having undergone C-S bond scission; however, three distinct sulfur states were observed for all samples in the XPS of the S 2p region. The lowest- and highest-binding-energy components are assigned to alkylthiolate and partially oxidized alkylthiolate species, respectively. The remaining S 2p component (approximately one-third of the sulfur layer), intermediate in binding energy between the other two components, is attributed to a chemisorbed species with a S binding configuration distinct from the majority alkylthiolate: for example, S bound to Pt bound to O, S with a different Pt coordination number, or S in an adsorbed disulfide. 相似文献
160.
Dmitri E. Kharzeev Yuta Kikuchi René Meyer 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(5):83
We describe a new type of the chiral magnetic effect (CME) that should occur in Weyl semimetals (WSMs) with an asymmetry in the dispersion relations of the left- and right-handed (LH and RH) chiral Weyl fermions. In such materials, time-dependent pumping of electrons from a non-chiral external source can generate a non-vanishing chiral chemical potential. This is due to the different capacities of the LH and RH chiral Weyl cones arising from the difference in the density of states in the LH and RH cones. The chiral chemical potential then generates, via the chiral anomaly, a current along the direction of an applied magnetic field even in the absence of an external electric field. The source of chirality imbalance in this new setup is thus due to the band structure of the system and the presence of (non-chiral) electron source, and not due to the parallel electric and magnetic fields. We illustrate the effect by an argument based on the effective field theory, and by the chiral kinetic theory calculation for a rotationally invariant WSM with different Fermi velocities in the left and right chiral Weyl cones; we also consider the case of a WSM with Weyl nodes at different energies. We argue that this effect is generically present in WSMs with different dispersion relations for LH and RH chiral Weyl cones, such as SrSi2 recently predicted as a WSM with broken inversion and mirror symmetries, as long as the chiral relaxation time is much longer than the transport scattering time. 相似文献